Modern History of Volcano Observation in Japan : Especially Volcano Surveillance of Japan Meteorological Agency

Abstract

Volcano observation is a basic to the fundamental research on volcanism and to the surveillance of volcanic activity for disaster mitigation. In this paper, the author reviews the history of volcano observation in Japan since 19th century, especially the history of volcano surveillance of the Japan Meteorological Agency (JMA) and the recent advancement of the monitoring technique of JMA. The volcano observation in Japan started by Prof. Sekiya on occasion of the eruption of Bandai volcano in 1888. Prof. Omori carried out pioneering observation at Usu volcano in 1910 and established the first volcanological observatory at Asama volcano in 1911. Since then, national universities established observatories at several active volcanoes. Their recent volcanological researches have been endorsed by the National Project of the Prediction of Volcanic Eruptions that started in 1974. JMA's continuous volcano observation started in 1888. JMA had started continuous observation at 10 volcanoes by 1950. In 1962-66, JMA divided active volcanoes into three classes (A, B and C) depending on the level of volcanic activity and the risk of disaster and installed seismographs at three and one stations for A class (4 volcanoes) and B class volcanoes (13 volcanoes), respectively, and organized mobile observation teams for B and C class volcanoes. Since late 1980’s, public concern for volcanic disaster mitigation has risen because of the eruptions at Izu-Oshima volcano in 1986, Unzen volcano in 1991, Usu volcano and Miyakejima volcano in 2000. To promote the disaster preparedness, JMA strengthened observation system and established Volcano Observation and Information Centers (VOIC) at Sapporo, Sendai, Tokyo and Fukuoka and centralized the volcano observation in 2001. VOIC installed TV cameras, seismometers, GPS stations, tiltmeters and infrasonic stations at each volcano. Most of the TV cameras are as sensitive as to detect visual phenomena even at night. These data obtained at each station are telemetered to VOICs and are monitored on a real-time in 24 hours. Each VOIC has Mobile Observation Team, which periodically collects basic observational data from active volcanoes. The observations consist not only of the installation of temporal observation stations but also of periodical thermal, geomagnetic and geodetic surveys. They carry out temporal observations to enhance monitoring capability whenever an unusual phenomenon is detected at volcanoes. VOIC issues Volcano Information to the disaster prevention authorities and to the public to initiate and take relevant disaster mitigation measures. There are three types of Volcano Information, Volcanic Alert, Volcanic Advisory, and Volcanic Observation Report. Since November 2003, JMA has introduced Volcanic Activity Levels as an additional index to Volcano Information for some volcanoes. To indicate the Level, JMA uses 6-level of numerical scheme to reflect an increasing order of unrest: 0 as dormant to 5 as large-scale eruption.